Re: [Help-bash] Bash Trap: How to Get Line Number of a Subprocess with Non-Zero Status

[Steve Amerige]

On 12/30/2016 12:50 PM, Chet Ramey wrote:

> It's the difference between a simple command, which has a line number, and
> a subshell command, which does not.  The subshell command's line number is
> derived from the execution context, which is relative to the start of the
> function.  The OP wants the subshell's line number to be absolute, like the
> simple command's, and not relative to the start of the function, as it is
> now.
>     
    
    From an end-user's perspective, it is unexpected that the LINENO has
    the value of the
    beginning of the function instead of the line at which the ERR was
    caught by trap.
    While the "inside" of the subshell might have it's own
    characteristics, the inside must
    eventually meet the "outside" of the subshell... at which point, an
    end user can reasonably
    expect that an error is reported in a common-sense way with the line
    number that is
    seen in the script file itself. While the current behavior can be
    explained, that doesn't
    mean it is expected by end users or makes sense.
    
    Using any other line number for LINENO also makes it harder to debug
    scripts, of course,
    since the line number being reported isn't as helpful.
    
    Is there any way this can be fixed... or introduced as a feature
    (e.g., with some
    set -o or shopt flag)?  A fix would help out a significant number of
    people. As it is, a
    workaround now is to use:
    
        $(...)
    
    instead of:
    
        (...)
    
    to get the expected behavior. But, this can mean some significant
    re-writing of code.
    
    Enjoy,
    Steve Amerige
    Server Science Incorporated
    Eggsh:
        A Powerful and Reusable Bash Scripting Platform, an Open-Source
        Project